The proposed research is intended to characterize further our purified preparation of the catecholamine synthesizing enzyme dopamine-beta-hydroxylase (DBH) as it pertains to humans. We have isolated DBH from normal human plasma, initiated characterization studies, and harvested large amounts of antibodies to the enzyme. Our present goals include: 1) Further characterization of the purified normal plasma enzyme; 2) Comparison of normal human DBH to the enzyme from other sources; 3) Further facilitation of isolation with additional affinity chromatography procedures; and 4) Further testing of the usefulness of plasma DBH activity as an index of adrenergic function using a variety of techniques including the development of a radioimmunoassay for DBH. Human plasma DBH has been purified over 6,000-fold and characterized according to molecular weight, subunit structure, kinetic and immunologic properties. Further studies will be directed toward isolation of DBH from human adrenal glands, pheochromocytoma tumors, and other species. All forms of the enzyme will be characterized further regarding behavior in the analytical ultracentrifuge, copper content, carbohydrate composition, and kinetic properties. A radioimmunoassay (RIA) will be developed with our purified enzyme, and this will be used for comparison with our clinical studies using the enzymatic assay. Studies will be performed in normal subjects and patients with varying forms of hypertension. Immunologic and enzymatic activity will be compared with results of catecholamine assays and the response to infusion of phentolamine (alpha blocker).